Explosive materials are classified into explosives used for blasting and the like, and combustion compositions which give off gas and heat while burning without an outside supply of air or oxygen. Generally, examples of the explosives include nitroglycerin-containing dynamite, ANFO prepared by mixing ammonium nitrate with fuel oils, PBX (Plastic Bonded Explosives) prepared by binding hexogen (RDX) or octogen (HMX) with polymeric binders, and bursting explosives containing trinitrotoluene, RDX or HMX as a major component. These compositions may easily be exploded by means of detonators or fuses. On the other hand, examples of combustion compositions include difficult-to-detonate gun and rocket propellants, which are prepared by mixing solid oxidizers such as ammonium perchlorate, ammonium nitrate, HMX, RDX and the like with polymeric binders, nitrocellulose, or the like. Research has been performed up to the present with the goal of improving the performance of these propellants by seeking for and developing materials having a high energy density per unit of weight or volume. One means of achieving this is by using high energy density materials such as hexanitrohexaazaisowurtzitane, hexanitrohexaazaadamantane, octanitrocubene, or the like. An example is given in pages 228 and 229 of a paper distributed at the Energetic Materials Summer Conference of Jul. 25, 1989 that CL-20 described in the "Critical Technology Plan" edited by the USDOD (United States Department of Defense), which is noted in the February 1992 issue of "Boei Gijutsu (Defense Technology Journal)", is hexanitrohexaazaisowurtzitane. According to the paper, hexa-nitrohexaazaisowurtzitane has a density of 1.98, a detonation pressure of 432 Kbar and an energy density of 455 cal/cm.sup.3. From this it follows that hexanitrohexaazaisowurtzitane has a density higher by ca. 4%, a detonation pressure higher by ca. 10% and an energy density ca. 4.2 times higher than those of HMX (density: 1.90, detonation pressure: 391 Kbar, energy density: 109 cal/cm.sup.3), which has been superior in performance to any other conventional explosive materials.
The sensitivity of hexanitrohexaazaisowurtzitane is amost equal to that of HMX in the condition in which it is usually produced, but higher than that of HMX in a certain crystalline form, so that precaution is required for its handling. Attempts have been made to lower the sensitivity by use of inert plasticizers, but there still remain problems such as separation of hexanitrohexaazaisowurtzitane from the inert plasticizer due to mutual incompatibility and deterioration of performance in terms of ignitability, combustibility, detonability and the like because of inertness of the plasticizers.
It is accordingly an object of the present invention to provide explosive compositions which are improved in handling safety without degrading performance in terms of ignitability, combustibility, detonability and the like by selection of plasticizers that have good compatibility with hexanitrohexaazaisowurtzitane while lowering the sensitivity.